1. Field of the Invention
The present invention relates to an ultrasonic distance-measuring sensor assembly and an ultrasonic distance-measuring sensor thereof, and in particular relates to an ultrasonic distance-measuring sensor assembly and an ultrasonic distance-measuring sensor thereof with a plurality of independent ultrasonic generating/receiving unit.
2. Description of the Related Art
Conventionally, an ultrasonic distance measuring sensor system is composed of two transducer units. One is an ultrasound generated unit and the other is an ultrasound received unit. These units are included an aluminum member whose inner surface was stuck by a piezoelectric plate as an actuator or a sensor. Thus, if the conventional ultrasonic distance-measuring sensor is applied to measure distance, for example car reversal radar, at least two ultrasonic transders are simultaneously used. Normally, one ultrasonic emitter generates an ultrasonic signal, and the other ultrasonic sensor receives the ultrasonic signal for measuring distance.
When considering application and cost, most ultrasonic distance-measuring sensors use a single unit to generate and then receive reflected ultrasonic signals from the barrier. A switch is added into the ultrasonic distance-measuring sensor to switch between a generating and a receiving current route, thus controlling the piezoelectric plate to generate or to receive the ultrasonic signal. After the ultrasonic distance-measuring sensor generates several ultrasonic waves with a period, the switch is switched to a receiving mode, and then a vibrating/sensing surface stops vibrating. However, after the reverberation time, the vibration is completely stopped, and then a vibrating/sensing surface starts to receive the ultrasonic waves reflected by a barrier. The detected distance due to the reverberation time and the velocity of the ultrasonic wave is defined as a dead zone of the ultrasonic distance-measuring sensor. That is, when the distance between the ultrasonic distance-measuring sensor and an object is less than the distance transformed according to the reverberation time and the velocity of the ultrasonic wave, the reflected signal is mixed with the reverberation signal. Thus, the object can not be discriminated. Specifically, the conventional ultrasonic distance-measuring sensor operates with the dead zone.
Meanwhile, when applied to the automobile industry, the ultrasonic distance-measuring sensor detects a wide horizontal area and narrow vertical area. The ultrasonic wave reflected by a distant barrier is not distinguished from the wave reflected by the ground in the time domain. Thus, the ultrasonic distance-measuring sensor is designed to generate an anisotropic beam.